The invention relates to a foldable wheelchair with lateral frames, on which there are supported drive- and travelling wheels, and folding means, such as a folding mechanism pivoted on a rotation axle disposed betwen the frames in a direction of travel.
Such foldable wheelchairs are intended for persons whose walking is impaired, sick persons, persons paralyzed in mid-section etc. In a known wheelchair of this type (DE-OS No. 1 943 339) the folding mechanism consists of cross-connected connecting rods and movable at the crossing point about the rotation axis in a scissor-like manner. So that all wheels may remain on the ground on moving across uneven terrain surfaces, this known wheelchair lacks a rigid connection between both frames. For this purpose the connecting rods are not only articulatably supported on the corresponding frame, but additional telescopically formed joints are provided, to permit transverse displacements between the connecting rods and the crossing point, when the wheelchair travels over uneven terrain. These articulated joints must have a high stability and be able to change their position continuously about their longitudinal axis, for which reasons additional spring elements are required. In a further known wheelchair (FR-OS No. 2 359 601) the vertical frame parts are formed telescopically for this purpose, and are also provided with spring elements.
This construction of known wheelchairs has led to the fact that these have today a weight of at least 20 kg, and that based on their expensive construction it is practically impossible to fall below this minimum weight. Furthermore these known wheelchairs convey a spongy travel feeling, because they are twistable within themselves during travel on uneven terrain in all directions, based on the large number (at least twenty) of joints, which makes the wheel chair traveller miss the correct contact with the terrain, on which he just happens to travel. Furthermore the known wheelchairs, based on the multiplicity of their joint connections, and their consequently unavoidably complicated construction, are subject to a strong wear, which causes in turn a considerable maintenance-and-repair-effort.